Known centrifugal pumps for medium to high consistency fiber suspensions--in the range, by way of example, of approximately 6 to 20 percent for paper pulp which is a typical application for such pumps--suffer from an inherent operational deficiency which seriously detracts from the efficient volumetric pumping of suspension material therethrough. The fluidization of the suspension by the rotating impeller blades in the inlet channel of the pump creates a strong turbulent, fluidized, annular layer of pulp adjacent the peripheral wall of the inlet channel. The suction effect of such centrifugal pumps cause this annular layer to flow substantially axially toward the working vanes in the pump interior, particularly when the pump is operating at relatively high capacity. At lower capacities, however, there develops a reverse or back flow of the fluidized pulp layer closest to the peripheral wall of the inlet channel thus decreasing volumetric flow of suspension through the centrifugal pump and correspondingly lowering the unit's operating efficiency.
It is accordingly the desideratum of the invention to provide a centrifugal pump for medium to high consistency suspension wherein reverse or back flow of suspension in the inlet channel is substantially eliminated. It is a particular object of the invention to provide such a pump in which the operating efficiency of the pump is notably increased without undue modification of the basic structure of the pump.
Other objects and features of the present invention will become apparent from the following detailed description considered in conjunction with the accompanying drawings. It is to be understood, however, that the drawings are designed solely for purposes of illustration and not as a definition of the limits of the invention, for which reference should be made to the appended claims.